Sony Alpha QX1 has a APS-C sensor with dimensions of 23.2 x 15.4 mm and sensor area of 357.28mm2.
Sony QX1's sensor is 170% larger than the average Lens-style sensor in its class. In cases where all the other parameters are the same between two cameras, the one with the larger sensor collects more light per pixel and performs better (less noise) in low light / High ISO conditions . Larger sensors also give the photographer more control on the depth of field.
Read our detailed Sony QX1 Review